
MICROORGANISMS : FRIEND AND FOE
21
commonly known antibiotics which are
made from fungi and bacteria. The
antibiotics are manufactured by
growing specific microorganisms and
are used to cure a variety of diseases.
Antibiotics are even mixed with the
feed of livestock and poultry to check
microbial infection in animals. They are
also used to control many plant
diseases.
It is important to remember that
antibiotics should be taken only on
the advice of a qualified doctor. Also
you must complete the course
prescribed by the doctor. If you take
antibiotics when not needed or in
wrong doses, it may make the drug
less effective when you might need
it in future. Also antibiotics taken
unnecessarily may kill the beneficial
bacteria in the body. Antibiotics,
however, are not effective against
cold and flu as these are caused by
viruses.
Vaccine
from the disease-causing microbes for
ever. This is how a vaccine works.
Several diseases, including cholera,
tuberculosis, smallpox and hepatitis can
be prevented by vaccination.
Edward Jenner
discovered the
vaccine for small-
pox in 1798.
Why are children/infants
given vaccination?
When a disease-carrying microbe enters
our body, the body produces antibodies
to fight the invader. The body also
remembers how to fight the microbe if
it enters again. If dead or weakened
microbes are introduced into a healthy
body, the body fights and kills
the invading bacteria by producing
suitable antibodies. The antibodies
remain in the body and we are protected
In your childhood, you must have
been given injections to protect
yourself against several diseases.
Can you prepare a list of these
diseases? You may take help from
your parents.
It is essential to protect all children
against these diseases. Necessary
vaccines are available in the nearby
hospitals. You might have seen the
advertisement on TV and newspapers
regarding protection of children against
polio under the Pulse Polio Programme.
Polio drops given to children are
actually a vaccine.
A worldwide campaign against
smallpox has finally led to its eradication
from most parts of the world.
These days vaccines are made on a
large scale from microorganisms to
protect humans and other animals from
several diseases.
Increasing Soil Fertility
Some bacteria (Fig. 2.7) are able to fix
nitrogen from the atmosphere to enrich
soil with nitrogen and increase its
fertility. These microbes are commonly
called biological nitrogen fixers.